This invention relates to the draining of water from flat roofs, balconies, decks and other flat or low sloping surfaces that are covered with a water-tight single layer synthetic roofing and waterproofing membrane.
The term "flat or low sloping surfaces" is not limited to surfaces that are perfectly flat. Very few roofs and other surfaces are perfectly flat due to intentional pitch, variations in thickness of construction materials, or sagging over time. Some roofs are deliberately pitched toward the drains so that the water is directed toward the drains. Some architects and roofing contractors rely on evaporation to take care of water that accumulates in low areas. All these roofs visually appear to be flat and are included within the term "flat surfaces". Similarly, decks and balconies rarely are perfectly flat although they visually appear flat. They are not flat for the same reasons flat roofs are not perfectly flat. Hence, the terms "flat" or "low sloping" is used in reference to a roof, balcony or deck with a pitch from 1/16 to two inches per foot.
Many commercial and residential buildings have flat roofs. Until recently, these buildings were weather protected with conventional asphaltic built-up felt membranes or modifications of such systems. Roof drains for these buildings are predominantly made of cast and malleable iron or steel materials. The drains usually consist of a drain bowl, deck and clamping rings, and a strainer cap. When the drain is installed, nails, screws or other mechanical fasteners are used to connect the drain parts to the roof. In addition, sheet metal or lead flashing is used to make a seal around the drain with multiple layers of asphalt felt placed under and over the outer perimeter of the sheet metal or lead flashing and coated with liquid asphalt.
In recent years, single layer sheets of synthetic rubber- , vinyl-, polyethylene- or polypropylene-based materials have become popular alternatives to built-up asphalt roofing. Roofs drains, however, have largely remained unchanged. Many of the drains still consists of cast and malleable iron or steel materials that are nailed, screwed or otherwise mechanically connected to the roof and sealed with sheet metal or lead flashing, asphalt sealing materials and clamping devices. Others consist of sheet metal pans laminated with synthetic rubber, vinyl or polyethylene or polypropylene membranes, and conventional cast iron drain assemblies comprised of a strainer cap, clamping rings or flanges and a drain pipe. An example of this latter technology is shown in U.S. Pat. No. 4,112,632.
More recently, drain devices made of synthetic rubber, vinyl, polyethylene or polypropylene have become available. These drain devices require extensive field assembly using mechanical clamping devices that attach and seal the drain to the roof by penetrating the synthetic membrane roofing material with screws, nails or other fasteners and, in some instances, laminated metal flashing materials.